IMO Frank Gruber was one of the best of the pulp writers and
his Johnny Fletcher and Sam Cragg novels are the equal to any
series from the 30s, 40s and 50s. His early non-series novels
are worth picking up, too. The Cold War books, as has been
mentioned, aren't very good, though I'm particularly fond of
"The Twilight Man."

"The Gamecock Murders" is entertaining and definitely worth
reading, but not quite in the same league as some of the best
(again IMO) Fletcher-Cragg books, notably "The Honest Dealer"
or "The Limping Goose." The format for the series was that
Fletcher and Cragg, two raffish "book salesmen" always on the
run from either cops or bill collectors, stumble into a sort
of closed societal grouping, cultural or professional, where
murder is committed. In "Dealer," it's the Las Vegas casino
world. "Goose" involves both numismatology and collection
agencies. "Gamecock," originally titled
"The Scarlet Feather," puts the pair into the illegal
cockfight milieu. It's origin is "Death At The Main," a short
story that Gruber wrote for Thrilling Detective that featured
his pulp hero Oliver Quade the Human Encyclopedia. It's
included, along with nine other Quade stories and a
fascinating essay by Gruber about his pulp years, in the 1966
collection "Brass Knuckles"
(Sherbourne Press) that is, unfortunately, long out of
print.

This is probably more than you'd want to know about
"Gamecock" and/or Gruber but we can't keep talking about
Ellroy forever.